Although not limited to this type of vehicle, the invention will be more particularly described with reference to vehicles of the “civil engineering” type, for example dumpers intended for mining use. It notably concerns vehicles that may be required to run at the maximum of their capabilities and thus travel permanently within a mine for mine productivity reasons.
These vehicles usually comprise a steering front axle system comprising two steering wheels and a rear axle system, more often rigid, comprising four drive wheels divided into pairs on each side. An axle system is defined as a set of elements for linking the fixed structure of the vehicle to the ground.
In the case of these vehicles, notably intended for uses in mines or quarries for transporting loads, access difficulties and efficiency requirements are leading the manufacturers of these vehicles to increase their load capacity. It follows that the vehicles are increasingly large and therefore themselves increasingly heavy and can transport an increasingly heavy load. The current weights of these vehicles can be as high as several hundred tonnes and the same applies for the load to be transported; the overall weight can be as high as 600 tonnes.
Since the load capacity of the vehicle is directly linked to that of the tires, the design of the tires must be adapted to these trends to provide tires capable of withstanding the usage stresses.
The dimensions of these tires are therefore large. Consequently, the dimensions of the wheels are also large and the stiffness of the bottom regions of the tires is such that said wheels have to be made in several parts to enable the tire to be fitted onto a rim. The fitting and removal of the tires that take place during replacement or servicing involve long and tedious handling operations. The number of fastening parts that have to be handled during these operations may be greater than 200, and then there are the associated very significant tightening torques for these parts. These operations therefore take a long time which is detrimental to the productivity sought in the work of operating these mines.
With the current demand always geared towards increasing the load capacity of these vehicles, the various parameters mentioned previously are leading the designers of tires to optimize said tires, notably by taking into account their use.
To meet the demand of the users who want an even greater increase in the load capacity of the carrier vehicles, used notably in mines, it is necessary to improve the efficiency of the tires.
For this, it may be necessary to temporarily associate measurement means for measuring characteristics associated with the stresses withstood by a tire fitted on a running vehicle; these are characteristics measured directly on the tire and/or characteristics influencing the stresses that the tire withstands when the vehicle is running. These measurement means will make it possible to follow what the tires fitted on such vehicles undergo, and thus enable the designers of tires to be able to better adapt the tires to the real-life uses and meet the demands of the users, notably in terms of transported load capacity.
Such measurement means are, for example, means for measuring pressure and temperature, means measuring speeds, accelerations, and so on.
Since these measurement means are put in place temporarily and the down times of the vehicles are detrimental to productivity, they are designed to be easily and rapidly fitted or removed.
For this, they are also advantageously designed to be of modest sizes and weights so as to be easily transportable.
They are also designed to operate autonomously and therefore for each to have an associated energy source.
This energy source, in order to further limit the weight, is reduced to the maximum from the mass and bulk point of view and consequently is limited in terms of power.
The temporary association of measurement means for measuring characteristics associated with the stresses withstood by a tire fitted on a running vehicle consequently dictates measurement means which, on the one hand, are not linked together or even to an energy source by wired links in order to simplify the transportation, the fitting and then the removal of said measurement means; indeed, it is essential to limit the down times of the vehicles and therefore provide for installation and dismantling that are as simple and rapid as possible. On the other hand, it dictates an absence of communication between the measurement means by wireless links and therefore by waves, such communication techniques being heavy consumers of energy. It is also difficult to design a roaming system that operates on the principle of communication by radio waves, bearing in mind that this type of communication means is regulated and that the rules, and more particularly the frequencies, may vary from one country to another.
In the present case, the desire to obtain data relating to the stresses undergone by the tire necessitates a plurality of measurement means in order to obtain information that is as comprehensive as possible. It is also necessary, for the analysis of such data, to be able to combine all the measurements and therefore synchronize them.